The Mobile Internet Protocol (MIP) represents a network-level approach for supporting the mobility of mobile stations across various networks and/or sub-networks. When a mobile station moves from its home network to operate in a foreign network, a home agent associated with the mobile station tunnels data packets destined for the mobile station to a Care-of-Address (CoA) associated with the mobile station. The CoA may be associated with a mobility agent (e.g., a foreign agent). Data packets destined for the mobile station can then be tunneled to the mobility agent and, subsequently, to the mobile station.
In previous systems, mobility agents sent advertisements to advertise their presence to mobile stations. When the mobile station detected a change in a mobility agent through the receipt of the advertisement, the mobile station sent a MIP registration request through the new mobility agent to the home agent. In other words, the mobile station was required to conduct a MIP registration each time it changed mobility agents.
While providing for mobility agent changes, these previous approaches had several problems, which were particularly acute when the mobile station's connection to the network was a wireless connection. For instance, multiple MIP registrations wasted valuable system resources that could be used for other purposes. Consequently, handover latency became poor in many of these previous systems. In addition, the multiple registrations that occurred increased the possibility of losing messages. Message loss became particularly acute if the wireless connection deteriorated immediately before or after a handover occurred, further degrading system performance.
Other approaches, such as using proxy mobility agents, were devised in the context of providing MIP-like service to mobile stations that were not themselves capable of providing MIP functionality. However, these approaches did not alleviate the problems described above for mobile that were inherently capable of providing MIP functionality. As such, these later approaches were still vulnerable to packet loss where the Radio Frequency (RF) conditions before and after the handover were poor.
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